A Look at minit

Sys-V init has long been the standard solution for booting. It's kind of easy to work with, it kind of works and everybody kind of knows it. However, being open minded, let's look at an alternative approach.

There are quite a few alternatives. All of them focus on improving boot times. This is accomplished by starting and running different processes simultaneously and asynchronously. Doing type of boot attempts to use all (more) parts of the hardware simultaneously and avoid having to wait for slow hardware.

In an embedded setting, one more factor to look for is keeping the footprint and number of processes down (each process comes with an overhead - albeit small).

One of the alternatives that I've looked at is minit by Felix von Leitner of diet-libc fame. What can it do? Well, the most basic feature is that it can start services and takes dependencies into account, e.g. it waits for the network to be up before it starts the web server. It also does respawning and handles ctrl+alt+delete.

Being the brain child of von Leitner, it is also minimalist (to the extreme?) and works with diet-libc. So, how does it work?

The configuration lives in /etc/minit, where each sub-directory contains one or services. Each service is configured from a number of symlinks and text files, all listed in detail in this howto. Basically, you create a symlink called "run" pointing at the program to start, a text file called "depends" with the names of any prerequisite services, an empty file called "respawn" if the service is to be respawned upon termination, and so on.

Having configured all your services, create a directory called "default" and add a depends file there listing your services. That will kickstart the system.

Image courtesy of http://www.flickr.com/photos/livingos/ / CC BY-SA 2.0. Original: at Flickr.

______________________

Johan Thelin is a consultant working with Qt, embedded and free
software. On-line, he is known as e8johan.

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Upstart

Hey! Dojo's picture

The major distributions (Fedora and Ubuntu at least and I suspect OpenSuSe too) Started using upstart a while ago instead of sysvinit. I believe upstart is also used by a certain Linux based smart phone operating system beginning with A, owned by a company you might have heard of beginning with G.

Upstart is a big contributing factor towards why the Ubuntu LTS release boots in under 20 seconds on a netbook sporting an SSD.

While the upstart developers have not yet reached their goals for a 1.0 release, upstart is very stable, widely adopted and supported by Canonical.

It is event based so it has much greater flexibility than minit.

http://upstart.ubuntu.com/

OpenRC: http://roy.marples.na

Anonymous's picture

Thanks for the tip!

Johan Thelin's picture

Thanks for the tip! I'v allready googled up the pages and added to my TODO surfing queue :-)

Johan Thelin is a consultant working with Qt, embedded and free
software. On-line, he is known as e8johan.

That's cool init, but nothing

Anonymous's picture

That's cool init, but nothing prevents you from taking look at / using outstanding OpenRC package being developed mainly for Gentoo Linux, but also with very strong pressure put on usability in containters like OpenVZ, LXC etc.

OpenRC is small, fast, nice and easy to use.

Brilliant

John Knight's picture

What a lovely introduction and an interesting alternative - well done, Johan. :)

John Knight is the New Projects columnist for Linux Journal.

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